Three-dimensional (3D) bioprinting shows great potential for autologous vascular grafts due to its simplicity, accuracy, and flexibility. 6mm diameter vascular grafts are used in clinic. However, producing small-diameter vascular grafts are still an enormous challenge. Normally, sacrificial hydrogels are used as temporary lumen support to mold tubular structure which will affect the structure’s stability. In this study, we develop a new bioprinting approach to fabricating small-diameter vessel using two-step crosslinking process. ¼ lumen wall of bioprinted gelatin mechacrylate (GelMA) flat structure is exposed to ultraviolet (UV) light briefly for having certain strength, while ¾ lumen wall shows as concave structure remained uncrosslinked. Pre-crosslinked flat structure is merged towards the uncrosslinked concave structure. Two individual structures will be combined tightly into an intact tubular structure by receiving more UV exposure time. Complicated tubular structures are constructed by these method. Notably, the GelMA-based bioink loaded with smooth muscle cells (SMCs) are bioprinted as the outer layer and human umbilical vein endothelial cells (HUVECs) are seeded onto the inner surface. A bionic vascular vessel with dual layers is fabricated successfully and keeps good viability, and functionality. This study may provide a novel idea for fabricating biomimetic vascular network or other more complicated organs.
